The invention relates generally to signalling the establishment of connections in connection oriented networks, for instance through the use of a management entity such as a call processor. More particularly, the invention relates to methods and apparatus for signalling the establishment of connections across ATM networks over a proxy signalling interface, for instance a user network interface or the like.
Signalling protocols are often deployed to establish or set up connections so as to form an end to end path for a call in a communications network. Signalling in connection oriented networks is the process of establishing, maintaining and releasing a connection through the exchange of connection establishment request, connection acknowledgement, and connection clearing messages between the network elements along a given message path. At times, however, the originating calling equipment does not have the necessary network capabilities to signal a call in a given network through which a call must be routed. For instance, an intermediate network may not directly support the signalling protocols of the preceding and succeeding networks. As a result, an off-board call processor or network management device may be utilized to interface with the signalling of the proceeding and succeeding networks and to control the elements of the intermediate network. To control the intermediate network, the call processor or network manager must be able to efficiently establish connections across the intermediate network.
Communications networks may have particular or unique signalling protocols for setting up connections for calls, which signalling protocols may be unavailable to a succeeding network through which call establishment is to be propagated. In a communications environment of shared network resources, it is not uncommon for communication service providers to buy or rent access to bandwidth on a third party network from a network provider and use the third party network for the transmission of customer traffic. For instance, the introduction of competition in certain jurisdictions of the telephone industry has led to the creation of new competitors which are typically smaller or less capitalized than the former telephone monopolies. As well, these new competitors may sometimes offer more specialized or more restricted services than do the former monopolies. Often the newcomers to the telephone industry may not own end to end networks for carrying customer traffic. These newcomers may instead provide local networks that can connect customers to a backbone infrastructure, which in turn provisions connections to other local networks connected to the backbone. Alternatively, communication service providers may provide end to end communication systems but may wish to employ different types of networks within their systems. For example, a service provider may wish to establish local telephone networks employing traditional telephone communication technologies with interconnections between such networks being provisioned on high speed ATM networks. In all such cases, the signalling protocols of the various networks found along the call path may be incompatible or not supported from one network to another.
It is known in the art for a network management entity to be utilized in order to provision a connection path on behalf of another node across a connection oriented network. This may be implemented for purposes of establishing connections for or on behalf of equipment or networks which do not possess such capabilities, as described above, or for other reasons known to those skilled in this art. For example, it may be thought advantageous from the perspective of technology upgrades to dedicate the function of connection establishment and management to a network management entity. Typically, the goal of the network management entity is to provide path connectivity between ports in the network. The ports in question may be of various types, such as ATM ports, Frame Relay ports, Circuit Emulation ports, xDSL ports (such as ADSL, VDSL, HDSL and the like), and any other port types supported in the network being controlled. When the network management entity seeks to establish a path between two ports, it will normally dictate the channel number on each endpoint port. For example, the channel on a given port is a VPI/VCI for an ATM virtual circuit, a VPI only for an ATM virtual path, a DS0 for a T1 circuit emulation path, and a stream and DLCI for a frame relay path, to name but some examples.
Thus, when a given network is used to provide the backbone infrastructure for another originating network, it may be necessary to supply proxied connection establishment functions for the originating network. Whether for portions of the end to end call path which traverse the intermediate network or for the rest of the end to end path, the call set up is often administered on behalf of the originating network. This is typically done through an off board device or network management entity that is connected to the intermediate network. The off board device may be part of the signalling network for the originating network. The term xe2x80x9coff boardxe2x80x9d means that the device is not necessarily part of a switch or node in the intermediate network. By way of specific example, off board devices are at times required for establishing connections across ATM networks on behalf telephone networks because telephone networks have not always been capable of performing signalling over typical ATM networks. Thus, call establishment, maintenance and tear down must be provided by a separate device such as an off board call processor. A signalling protocol typically used in telephone networks is the SS7 protocol. Currently, the SS7 protocol is often not supplied within an ATM network switch. Thus, in the specific example given above, the off board device would convert the SS7 signalling instructions into call setup instructions which are understood in the ATM network. It will be appreciated that various methods for setting up calls in an ATM network from an off board device are known to exist.
The communications system 10 of FIG. 1 is a specific example of the use of an ATM network 12 as a backbone for an originating network such as a telephone network. The communications system 10 consists of first and second telephone networks 14, 16, the ATM network 12 and an SS7 signalling network 18. The SS7 signalling network 18 provides call connection control for the telephone networks 14,16. The SS7 signalling network 18 receives call setup requests from the telephone networks 14,16 and establishes connections for an end to end call path between the desired source and destination of the call by configuring the necessary switching in the nodes of the telephone networks 14,16. The establishment of connections in communications networks using the SS7 protocol is well known to those skilled in the art. As explained previously, there are situations where it is desired to make a connection across the ATM network 12 in order to establish an end to end path for a call, for example in the event that a caller at a first telephone 20 connected to the first telephone network 14 wants to make a call to a person at a second telephone 22 connected to the second telephone network 16, and where the ATM network may not directly support SS7 signalling. If so, another method is therefore necessary to establish such connections in the ATM network. Typically in these situations, an off board device such as a call processor or network management entity 24 is used to establish the connection across the ATM network 12 required to set up the call.
In some instances, the time that is required to set up proxied connections to define an end to end path for a call can affect network performance. The longer the time that is required to set up a call, the fewer calls that a network may set up every minute. In situations where hundreds or thousands of calls are required to be set up every second, the efficiency of the method used in setting up calls is important. If call set up rates are too low, customers may give up trying to make a call rather than wait for an impractical period of time.
As explained in greater detail below, various categories of proxied methods for setting up a connection across a communications network, for instance an ATM backbone network, are currently known. According to a first category, a call processor may be implemented for this purpose, whereby the call processor utilizes a management protocol for establishing connections through a network. Ideally the call processor understands the full topology of the network in question, such as the nodes in the network, the links interconnecting the nodes, and the current utilization of links in the network. Given the endpoints of the required path through a network, the call processor computes the path it desires through the network. Once the decision is made, the call processor sends a command or series of commands to each node involved in the call path to direct it to create a cross-connect between the ingress port and the egress port of such nodes. Each node is given a separate management command or series of management commands to create the relevant cross-connect. Taken together, the resulting series of cross-connects and internode links form a complete path across the network connecting a channel from an ingress point in the network to an egress point thereof. To delete the path, the call processor sends one or more management commands to each node involved in the previously established path to request that the cross-connect on each node be removed.
The management commands mentioned above are typically implemented using standard management protocols such as Simple Network Management Protocol (xe2x80x9cSNMPxe2x80x9d) or Common Management Information Protocol (xe2x80x9cCMIPxe2x80x9d), or may otherwise be executed via a proprietary management protocol implemented by the call processor and the nodes. A call processor will require a communication path for management commands for each node that it communicates with. For example, there could be a separate physical connection between the call processor and each node. Alternatively, the network may provide a method of routing management commands to nodes within itself, so that only a physical interface to one node is needed and then the commands can be routed internally in the network between the nodes using the links which connect the nodes.
The prior art according to the first category of proxied methods discussed above has been applied to various types of connection oriented networks. For instance, these teachings have been applied or are adaptable to a Frame Relay network, a narrow band circuit-switched network or other such networks. In the ATM network as shown in FIG. 1, a management protocol may be used to establish connections in the ATM network 12 by converting the originating signalling instructions into a set of management commands that are understood by the ATM network 12. In the specific example of an originating network which uses the SS7 signalling protocol, this conversion is done by the call processor 24 which acts as an interface between the SS7 network 18 and the ATM network 12. The call processor 24 receives the SS7 instructions from the SS7 network over an SS7 link 26 and uses the information in the SS7 signalling instructions to determine the cross-connects that are required to be made within various nodes of ATM network 12 in order to establish the end to end path for the call. The call processor 24 then sends a management command containing a cross-connect instruction to each node in the ATM network through which the call is to be routed. The management instructions are typically provided using the SNMP protocol, but alternatively may be provided by other management protocols such as CMIP. The connections established in this way by such management commands are called Permanent Virtual Connections (PVC). Typically PVC connections are used for connections that are required to be maintained for a relatively long period of time, i.e. days, months or even years.
The call set up procedure for establishing an end to end path for a call between the first telephone 20 and the second telephone 22 according to this first known category of methods for call establishment across a network will now be explained in more detail using the specific example of FIG. 1. First, the SS7 signalling network 18 will establish the necessary connections in the first telephone network 14 to connect the first telephone 20 to a bridge node 28 in the telephone network 14 which is connected to the ATM network 12. The SS7 signalling network 18 then provides SS7 instructions to the call processor 24 over the SS7 link 26. The information in the SS7 instructions would typically indicate that a connection should be made between the first bridge node 28 and a destination address, which the call processor 24 determines is currently best reached through a link (such as link 29) which connects to node 30 in network 16. Using this information in the SS7 instructions, the call processor 24 then issues SNMP management commands to those nodes in the ATM network 12 that will constitute the intermediate portion of the end to end call path. Thus, commands are sent to an ingress ATM node 34, a first intermediate ATM node 36 and an egress ATM node 38 to establish cross-connects within these nodes that will serially connect the first bridge node 28 to the second bridge node 30. Alternate paths may be established, for example, a second intermediate ATM node 40 could be used instead of the first intermediate ATM node 36. The SNMP management commands may be sent to the nodes in the ATM network 12 over management interfaces (not shown) between the call processor 24 and the nodes. These management interfaces may be provided over direct connections or may be routed through one or more nodes in the ATM network 12.
The establishment of a connection according to methods of the foregoing variety between the first and second bridge nodes 28, 30 requires several management commands to be sent to the various nodes in the ATM network 12. It will be appreciated that in situations where the connection is required to pass through more than only the three nodes of the example in FIG. 1, more management commands than described will be required to define the various cross-connects at each network node. Because the SNMP protocol was designed to set up PVCs that were intended to exist for long periods of time, the setup time associated with establishing cross-connects using SNMP is not usually a critical factor. As a result, the SNMP protocol tends to be unsuitable for applications where many temporary connections are required to be set up and cleared on an ongoing basis. Typically this method of using SNMP commands to establish PVCs is capable of routing only a few calls per second. It will be appreciated that these rates of call set up are unacceptable or disadvantageous for applications requiring fast call set up rates such as making backbone connections for high volume networks which may require call set up rates in the vicinity of hundreds of calls or more per second. Thus the management commands used for creation of cross-connections are cumbersome and are not optimized for a very high rate of cross-connection establishment or deletion.
Another disadvantage of this known first category of methods is that the call processor 24 must be provided with all the information about the topology of the ATM network 12 and needs to have the necessary computational capabilities in order to calculate the appropriate or optimal path through the ATM network 12 for the connection. This added complexity contributes to the relative slowness of this method and may give the call processor 24 more information about the ATM network 12 than is desirable for either the operator of the ATM network 12 or the operator of the telephone network, for instance, where these networks may be owned or operated by different persons.
According to a second category of known proxied methods for setting up connections in communication networks, signalling and routing intelligence is used within the network to establish paths from a source port and channel to a destination port and channel upon command from a call processor or network management entity. One example of these prior art methods is the Soft Permanent Virtual Circuit (S-PVC) feature of the PNNI protocol of the ATM Forum (xe2x80x9cPrivate Network-Network Interface (PNNI) Specification Version 1.0xe2x80x9d, Document No. af-pnni-0055.0000, dated March 1996 and produced by the ATM Forum Technical Committee; hereafter xe2x80x9cthe PNNI Specificationxe2x80x9d). In this second category of prior art methods, the network management entity does not typically compute routes in the network and communicate with every node along the prospective path. Instead, it selects one of the endpoints as the source of an S-PVC, and sends a management command over a management link to the source node communicating the details of the source endpoint (such as slot, port, VPI, VCI for an ATM source endpoint, for instance). As well, the management entity will provide the source node with the destination address of the destination port, along with the desired destination VPI and VCI (for a destination ATM endpoint, for instance). The management command sent to the node to request the creation of an S-PVC may be done via a standard protocol such as SNMP or CMIP, or via a proprietary protocol. Usually, the source node will launch an SVC call, using well known techniques, from the source node to the destination node. In the case of the PNNI protocol, known to those skilled in this art, the source node computes the path through the network and includes it in the signalling message to steer the call through the network. This is known as source routing. In other signalling technologies that could be employed in the network, the call may be routed in a hop-by-hop manner from the source node to the destination node.
Included in a typical signalling message is the Called Party number, which allows the call to be routed to the destination node, and which informs the destination node of the interface to terminate the call on. A signalling Information Element (xe2x80x9cIExe2x80x9d) known as the xe2x80x9cCalled Party Soft PVPC or PVCCxe2x80x9d in the case of the PNNI protocol, tells the destination node which channel to use on the destination interface. In the initial version of the PNNI protocol, this IE only allowed for the encoding of a VPI and a VCI value, which is suitable for cell relay (e.g. ATM) interfaces. Other interface types were handled by logically mapping their channel identifier into the VPI and VCI values available in the IE. For example, for Frame Relay interfaces, the DLCI could be carried in the VCI field. The PNNI standard is expected to be updated to allow other types of channel identifiers, such as DLCI for Frame Relay, to be carried in this IE in a standardized manner.
Not only does the network route and signal the call to the destination node according to the prior art methods of the second category, but in the case of an S-PVC connection the destination node will also automatically respond to the received call with a connect indication, which is signalled back to the originating node using the signalling infrastructure of the network. When the originating node receives the connect indication, it can notify the management entity over the management link that the path has been successfully created across the network. To provide for security, the network management entity may optionally also choose to send a command to the destination node for the S-PVC as well as to the source node which will send the call. In this way, when the S-PVC Call SETUP message reaches the destination node, the destination node may determine where the call originated in order to decide on whether it should accept the call and respond with a connect message, or whether the call is not expected and it should therefore reject the call and respond with a release message. However, this increases the amount of management commands that are required to set up or delete the S-PVC. To delete the path across the network according to the prior art methods of the second category, the network management entity sends a command over the management link to the source node to tell it to delete the S-PVC (and to the destination node over a separate management link if a command was previously sent to the destination node as well). The source node will release the call across the network by sending a release signalling message over the network signalling infrastructure. This will clear the call and its corresponding cross-connects across the network.
The second category of known methods for setting up connections will now be described with reference to the specific example of FIG. 1. In the ATM network 12, management commands are used to set up an S-PVC between the first bridge node 28 and second bridge node 30. Where the management commands follow the SNMP protocol, the S-PVC set up command contains information identifying the address of the ingress ATM node 34 in the ATM portion of the end to end call path (termed the xe2x80x9cCalling Partyxe2x80x9d) and the address of the egress ATM node 38 in the ATM portion of the connection (termed the xe2x80x9cCalled Partyxe2x80x9d). For instance, the SNMP S-PVC SETUP command may contain information identifying the virtual path identifier (VPI) and virtual connection identifier (VCI) for each of the channels connecting the first bridge node 28 and the second bridge node 30 to the first intermediate ATM node 34 and second intermediate ATM node 38, respectively. These VPI/VCI values are termed the xe2x80x9cCalling Party Soft PVPC or PVCCxe2x80x9d and xe2x80x9cCalled Party Soft PVPC or PVCCxe2x80x9d respectively. When the S-PVC setup command is received by a node in the ATM network 12, for example the ingress ATM node 34, the node uses signalling to establish the S-PVC between the endpoint channels. The nodes in the ATM network 12 are typically connected by a network-node interface (NNI) or other network signalling link. The network node interface is typically provisioned over a Permanent Virtual Channel.
Referring again to FIG. 1, the ingress ATM node 34 receives the SNMP S-PVC set up command from the call processor 24 and generates the S-PVC SETUP request message in accordance with the signalling protocol employed, based on the information received in the SNMP command. The S-PVC SETUP request message is then forwarded through the ATM network 12 in accordance with its particular signalling protocol and a connection path is established in the ATM network connecting the specified channel on ATM node 34 to the specified channel on ATM node 38, thus forming a connection between the first bridge node 28 and second bridge node 30. The use of signalling protocols to establish S-PVCs in ATM networks is known to those skilled in the art.
Compared to prior art methods of the first category, the prior art methods of the second category allow for less management commands to create or delete a path, especially as the number of the nodes through which the path will traverse increases. Also, the burden of computing the path across the network is removed from the network management entity and is charged to the network nodes. Although fewer management commands are required with these methods than with methods of the first type described above, the relative slowness of executing SNMP commands remains a problem for applications where the establishment of many calls per second is desired. Typically this second method allows for a call setup rate in the vicinity of tens of calls per second. Thus, prior art methods according to this second category may provide for higher performance, but the management commands used are still typically cumbersome and not designed for a very high rate of path creation and deletion.
According to a third category of prior art methods, the proxy signalling capabilities provided in the ATM Forum UNI protocol, namely Annex 2 of xe2x80x9cUser-Network Interface (UNI) Signalling Specification, Version 4.0xe2x80x9d, Document No. af-sig-0061.000, dated July 1996 (the xe2x80x9cUNI 4.0 Specificationxe2x80x9d) are utilized. An earlier version of this protocol was released in 1994 as xe2x80x9cUser-Network Interface (UNI) Signalling Specification Version 3.1xe2x80x9d, Document No. af-uni-0010.002 produced by the ATM Forum Technical Committee (the xe2x80x9cUNI 3.1 Specificationxe2x80x9d). Such known proxy signalling allows a management entity or call processor to provide a Switched Virtual Connection (xe2x80x9cSVCxe2x80x9d) signalling control for interfaces which do not have their own direct signalling. For example, a proxy signalling interface can control an ingress interface of an originating node in an intermediate network found along the end-to-end call path, as well as many other interfaces on the originating node. Likewise, another proxy signalling interface can control an egress interface with many other interfaces on the terminating node. This use of known proxy signalling is specific to the case where a network management entity is employed to control a network and set up and tear down connection paths, as in the prior art methods of the first category discussed above. An advantage of known proxy signalling methods of this third category is that the call processor 24 does not need to know all of the details about the ATM network 12 in order to establish a connection across the ATM network 12.
Where a network management interface according to the third category of known methods is used to connect a given channel and port for an originating node to a given channel and port for a terminating node, as in the previous prior art examples, the network management interface will be configured to control the exact channel number at both ends of the path. Since the selection of a channel number at each path endpoint is dictated by the network management interface, this decision is not made by the endpoint nodes. This behaviour of the network management interface is not a requirement of generalized proxy signalling, as described in the UNI 4.0 Specification, at Annex 2 thereof Since the proxy signalling link can control one or many physical ports, the signalling messages must be able to indicate which port is being controlled, along with the VPI and VCI for the connection. In ATM Forum signalling like the UNI 4.0 or PNNI protocols, this is done by signalling a VPCI value and a VCI value. The VPCI value is mapped to a port and a VPI. An example of this mapping is shown in the UNI 4.0 Specification, Annex 2, Section A2.4 (at page 89 thereof). The VPCI and the VCI are indicated in the Connection Identifier IE.
At the originating proxy signalling link, which spans the originating node of the intermediate network and the network management interface, the network management interface will send a Call SETUP message to the originating node in order to initiate the path across the network being traversed. The network management interface will dictate the specific channel number on a given endpoint port for the connection. In the UNI 4.0 Specification, a network management interface can dictate this channel number by including the Connection Identifier IE in the SETUP message sent over the proxy signalling link. The Connection Identifier will have a VPCI value, which the switch will map to a pre-defined port and a pre-defined VPI on that port. The Connection Identifier will also have a VCI value to be used on the port and VPI. Thus, the originating endpoint is fully defined by the network management interface. If UNI 3.1 signalling or IISP signalling is being used instead, then the particular node in question may be configured as the user-side of the protocol, and the network management interface may be configured as the network side of the protocol. This is required since in the UNI 3.1 or IISP protocols, only the network side of the protocol is allowed to include the Connection Identifier IE in a SETUP message. The IISP protocol is defined in xe2x80x9cInterim Inter-Switch Signalling Protocol (IISP) Specification Version 1.0xe2x80x9d, Document No. af-pnni-0026.000, dated December 1994 and produced by the ATM Forum Technical Committee, and is well known to those in this art (the xe2x80x9cIISP Specificationxe2x80x9d). The UNI 3.1 or IISP signalling protocols normally do not allow a VPCI to represent multiple ports, but as long as the network management interface and the switch agree on the mapping, the VPCI value can be used as per the UNI 4.0 specification.
Typically, the SETUP message sent over the proxy signalling link will also have the Called Party number of the destination. The Called Party number could represent a specific port on the destination switch, or it could represent a logical port or a group of ports. Upon receipt of the Call SETUP message over the proxy signalling link, the originating node of the intermediate network over which the connection is being established will signal the call across the network in the usual manner. At the destination node of the intermediate network, the Called Party number IE in the Call SETUP message will indicate a specific port or a group of ports. In either of these cases, the signalling link for the port or ports indicated will be a distinct return proxy signalling link which connects back to the same network management interface that is controlling the network. Thus, each of the originating and terminating nodes of the network being traversed will be connected to the network management interface via respective signalling links.
In the foregoing example, the network management interface will also dictate the exact destination channel as it did at the originating end. With UNI 4.0 signalling on the proxy signalling link, this can be accomplished by configuring the terminating node to act as a non-assigning side for calls sent over the signalling link to the network management interface. Then, when the Call SETUP message is sent by the terminating node to the network management interface, it will not include the Connection Identifier IE, and the terminating node will make no decision on what the destination endpoint should be. For UNI 3.1 or IISP signalling to the particular network node can again run the user side of the protocol, and the network management interface will run the network side of the protocol. In this way, the node will act as the non-assigning side and will not include the Connection Identifier IE in the SETUP message sent over the terminating proxy signalling link to the network management interface.
Upon receiving the Call SETUP message from the terminating node over the terminating signalling link, the network management interface can then proceed to select the channel that it wishes for the destination of the path being set up, and signal a CONNECT message back over the terminating signalling link to the terminating network node to indicate that the call is accepted. The CONNECT message contains the Connection Identifier IE indicating the VPCI and the VCI of the endpoint to use. The destination node will complete the connection with the selected channel (again, the VPCI maps to port and VPI, and the VCI is also provided for a VC-level path). The CONNECT indication is signalled back across the network over its signalling infrastructure and to the network management interface via the originating proxy signalling link which connects it to the originating network node. At this point, the network management interface knows that the path is connected end-to-end successfully.
To remove the established connection path, the network management interface sends a RELEASE message for the call over either of the respective proxy signalling links associated with the originating and terminating network nodes. The RELEASE message will next be signalled across the network and the cross-connects will be removed. The RELEASE message will propagate to the opposite proxy signalling link back to the network management interface (e.g. if sent out by the network management interface over the proxy signalling link associated with the originating node, it will be received over the proxy signalling link associated with the terminating node and vice versa).
In order to establish an end to end path for calls with proxy signalling according to the third category of known methods, the call processor 24 of FIG. 1 is connected to the ATM network 12 by a network interface signalling link (not shown) and may, for instance, send Call SETUP request messages on behalf of an external node connected to the ATM network 12 such as the first bridge node 28. Often a network node of an adjacent network may be connected to an ATM backbone network but cannot perform signalling on its own behalf For example, the signalling must be performed on behalf of the first bridge node 28 by the call processor 24 because the first bridge node 28 is not connected to the ATM network by a signalling link. Thus, in these or other proxy signalling arrangements, the call processor 24 uses the UNI signalling link channel to establish an SVC in the ATM network 12. The SVC SETUP request message contains a Called Party Information Element for identifying the destination ATM node for the SVC. However, the SVC SETUP may only be used to establish a connection to an ATM endpoint identifiable by a Called Party address. In the communications system 10 of FIG. 1, signalling links are not provided between telephone networks 14, 16 and the ATM network 12. Thus, ATM node 38 would be the called party for an SVC providing a portion of the end to end call path between the telephone 20 and telephone 22. Similarly, the ATM node 34 would be the calling party for such a SVC. UNI signalling may be used to establish an SVC between the ATM node 34 and the ATM node 38.
In methods according to the third category of known techniques, signalling is used instead of management protocols such as SNMP or CMIP to establish and remove paths across a connection oriented network. Such signalling protocols and the call processing logic used to handle calls are normally optimized for very high call establishment and tear down rates, and so these prior art techniques can potentially provide a very efficient and high speed method of establishing and removing paths in a connection oriented network. One issue with these prior art methods is that the network management interface has to somehow correlate the call which it launched over one proxy signalling link with a call which is later received over the same or a different proxy signalling link. A single proxy signalling link could result where the source and destination interfaces are on the same node. Moreover, the network management interface may be launching many such calls at the same time. Thus, some sort of scheme must be used to correlate a call sent to the network with a call received from the network where it is desired to use the prior art techniques of the third category.
One available method of correlation is to use an IE which is carried end-to-end across the network, such that it will be in the originated SETUP message and in the received SETUP message. In such an IE, the network management interface could encode some sort of identifier such that it can match up a SETUP sent with a SETUP received. For each path to be established, the network management interface has to send a Call SETUP message, then receive a Call SETUP message, then send a CONNECT message, and then receive a CONNECT message. In this way, proxy signalling work is done at both ends of the network. Moreover, other messages like CALL PROCEEDING or CONNECT ACK may also be involved at each end of the network according to the prior art techniques of the third category, as known to those skilled in this art. When the path is removed, a RELEASE is sent at one end of the network and a RELEASE is received at the other end of the network. Again, there are other messages like RELEASE COMPLETE as well which may be involved in signalling a connection. So, while the signalling interface can provide a much more efficient interface into the node and provide for much higher call setup and tear down rates, with the third category of prior art techniques the network management interface has to correlate the sent and received calls, and thus deal with the overhead of signalling at both ends of the network.
Based on the foregoing, it can be seen that there is a need for another method of establishing proxied connections across a connection oriented network, for instance where compatible signalling is not provided between an ingress or egress node in a connection oriented network and an adjacent network or network device. It would therefore be advantageous to provide a method and corresponding apparatus for proxied signalling that would seek to reduce the amount of signalling work undertaken by a call processor 24, to avoid signalling traffic to and from both the source and the destination network nodes, to avoid the necessity of having to correlate a call setup sent with a call setup received, and to be capable of fully specifying both the source and the destination endpoints over the originating proxy signalling interface. This is especially desirable if ATM backbone networks are to be used to provide connections for telephony networks or any other communications networks featuring high call volumes. And while it is often necessary to allow users of connection oriented networks to have some degree of control over call setup in connection oriented networks, at the same time it is desirable to reduce the complexity required of the user for establishing the connections in such networks. It is an object of the present invention to attempt to meet these varied needs with a proxied signalling method and apparatus which permits connection establishment across a connection oriented network, such as an ATM network, whether or not signalling is provided along the entirety of the end-to-end call path, as explained in greater detail below.
According to a first broad aspect of the present invention, there is provided a method for establishing a connection across a connection oriented network on behalf of an originating network element to enable communications between the originating network element and a destination network node, the destination network node being addressable in the connection oriented network, the originating network element being connected to a source network node in the connection oriented network by a source communications channel addressable in the connection oriented network, the connection oriented network having a signalling infrastructure employing a network signalling protocol for establishing connections within the connection oriented network, the method comprising the steps of: (a) generating a proxy connection establishment request message for requesting the establishment of the connection between the originating network element and the destination network node, the proxy connection establishment request message comprising information identifying the source communications channel; (b) sending the generated proxy connection establishment request message from a network controlling element to the connection oriented network over a proxy signalling link provided between the network controlling element and the signalling infrastructure of the connection oriented network; (c) receiving the proxy connection establishment request message at the connection oriented network over the signalling link; (d) extracting the information identifying the source communications channel from the proxy connection establishment request message so received and establishing a cross-connect at the source network node to the source communications channel identified in the proxy connection establishment request message; (e) generating a network connection establishment request message according to the network signalling protocol; (f) sending the generated network connection establishment message over the signalling infrastructure to establish a path between the source network node and the destination network node using automated signalling procedures according to the network signalling protocol; (g) sending a network acknowledgement message which confirms establishment of said path, said network acknowledgement message being sent according to the network signalling protocol from the destination network node to the source network node over said signalling infrastructure; (h) after said path is established, sending a proxy acknowledgement message which confirms establishment of said connection between the originating network entity and the destination node, said proxy acknowledgement message being sent to the network controlling element from the source network node.
According to a second broad aspect of the present invention, there is provided a network controlling element for signalling a connection across a connection oriented network on behalf of an originating network element to enable communications between the originating network element and a destination network node, the destination network node being addressable in the connection oriented network, the originating network element being connected to a source network node in the connection oriented network by a source communications channel addressable in the connection oriented network, the connection oriented network having a signalling infrastructure employing a network signalling protocol for establishing connections within the connection oriented network, a proxy signalling link being provided between the network controlling element and the signalling infrastructure of the connection oriented network, the network controlling element comprising: (a) a communications interface for receiving instructions for establishing the connection on behalf of the originating network element; (b) a proxy signalling interface for generating a proxy connection establishment request message, for transmitting the proxy connection establishment request message over the proxy signalling link to the signalling infrastructure of the connection oriented network, and for receiving a proxy connection acknowledgement message from the source network node which is indicative of the establishment of the connection; and wherein the proxy connection establishment request message comprises information identifying the source communications channel, the information identifying the source communications channel being extracted from the proxy connection establishment request message when same is received at the connection oriented network over the proxy signalling link, wherein a cross-connect is established at the source network node to the source communications channel identified in the proxy connection establishment request message and wherein a network connection establishment request message is generated according to the network signalling protocol and is sent over the signalling infrastructure to establish a path between the source network node and the destination network node using automated signalling procedures according to the network signalling protocol, whereupon the proxy connection acknowledgement message is sent to the network controlling element from the source network node.
According to a third broad aspect of the present invention, there is provided an apparatus associated with a source network node for establishing a connection across a connection oriented network between an originating network element and a destination network node via the source network node, the source network node and the destination network node being addressable in the connection oriented network, the originating network element being connected to the source network node by a source communications channel addressable in the connection oriented network, the connection oriented network having a signalling infrastructure employing a network signalling protocol for establishing connections within the connection oriented network, the source communications channel being identified in information included in a proxy signalling message consisting of a proxy connection establishment request message received by the apparatus over a proxy signalling link, the apparatus comprising: (a) a proxy signalling interface which sends and receives proxy signalling messages over the proxy signalling link; (b) a network signalling interface which sends and receives network signalling messages over the signalling infrastructure of the connection oriented network; (c) a call controller which extracts from the proxy connection establishment request message the information identifying the source communications channel, which establishes a cross-connect at the source network node to the source communications channel identified in the proxy connection establishment request message and which generates a network signalling message consisting of a network connection establishment request message according to the network signalling protocol, the call controller providing the network connection establishment request message to the network signalling interface which in turn sends the network connection establishment request message over the signalling infrastructure of the connection oriented network to thereby establish a path between the source network node and the destination network node; and wherein after the path between the source network node and the destination network node has been so established, the apparatus receives a network signalling message consisting of a network connection acknowledgement message from the destination network node over the signalling infrastructure and at the network signalling interface, following which the call controller provides a proxy signalling message consisting of a proxy connection acknowledgement message to the proxy signalling interface.